1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a facsimile apparatus, a printer for visualizing a still image as a hard copy, and more particularly, to an image forming apparatus of a type where a paper feed cassette and a paper feed tray are attached and drawn from the front of the image forming apparatus (this type will hereinafter be referred to as "front loading").
2. Description of the Prior Art
Of various imaging technologies, the electrophotographic technology, especially the Carlson process has become an established technology in the field of the image forming technology because of its characteristics: being a dry process and having rapid processability.
For practical use, paper processing mechanism for feeding a sheet to the image forming section is an important matter of the technology. To live up to the recent rapid development of the office automation, it is an important factor to reduce the size of an image forming apparatus. To meet such a trend, the basic structure having been employed from the beginning, i.e. a structure where paper feed cassettes are arranged on the right side of the apparatus has been reconsidered, and a front loading structure has been devised where a sheet is loaded and unloaded from the front surface of the apparatus. For example, an image forming apparatus shown in FIG. 1 is one of such image forming apparatuses of the front loading structure. On the front surface of a base 101, drawer type trays 102a to 102d are provided where cassettes for sheets of various sizes (B5, A4, B4) to be used are attached. A sheet of selected size is conveyed from the tray to the upper part through a paper conveying section 103 (indicated by broken lines). And, an image is transferred to the sheet at a transferring section of the image forming apparatus provided in a copying machine body 104, and is fixed at a fusing section. Then, the sheet is fed into a copy receiving tray 108.
FIG. 2 shows a condition where a front plate 109, a side plate 106 and an original cover 111 of this image forming apparatus are opened. In this situation, the paper conveying section 103 is seen on the side portion of the image forming apparatus which is disclosed by opening the side plate 106.
Sheet jam is one of the troubles that reduce copy productivity of an image forming apparatuses. For practical use, how rapid a jam state is removed to retrieve the normal state is important to increase the reliability of the apparatus. In the apparatus of FIG. 1, since the paper conveying section 103 is disclosed as shown in FIG. 2 by opening with a pull 107 a side plate 106 pivotably attached to the base 101 on a hinge 105, when sheet jam is caused, jammed sheets can easily be cleared so that the normal state is swiftly retrieved.
On the other hand, a demand for mass copying has been increasing recently, which has made it necessary that copying machines are provided with a cassette which holds a large number of sheets. The conventional apparatus shown in FIG. 1 does not have a space for attaching a drawer type tray that holds a large number of sheets.
In a prior art shown in FIG. 3, a door 11 is provided in front of a body of an image forming apparatus and a side plate is stationarily fixed. FIG. 4 schematically shows a main portion of the copying machine of FIG. 3.
In the copying machine of FIG. 3, to remove a jam state, first, the door 11 is opened to disclose a conveying portion 13 as shown in the figure, and then a guide plate 16 is opened by operating an opening and closing handle 12 in a space 15 provided in the copying machine body to separate pairs of conveying rollers 17 provided in correspondence with the trays 10.
In this copying machine, however, the space 15 for operation (for example, a space with a width of 150 mm to 200 mm) is required inside the copying machine in order to open the guide plate 16 and to thereby separate pairs of the conveying rollers 17. As a result, the size of the apparatus cannot be reduced and moreover the jam state cannot rapidly be removed.